Sorry to grave dig, but had I known this earlier it would have been helpful. This post is about the Decagon 5TM, which has two protocols, SDI-12 and DDI. The DDI is typical UART at 1200 baud, which you can read from any UART reader. I've tested it with an FTDI cable and know it works with a LoPy. You do however have to power cycle the sensor to get a new reading.

Note: This may not work on new Decagon 5TM sensors if you have changed the SDI-12 address to anything other than 0. Factory default is 0. If you have not used SDI-12 to communicate with the sensor then it should work as expected.

We used a mosfet to turn the power on and off for the sensor, controlled by GPIO. Reading the UART within 10s of milliseconds from turning the power on will give you your readings. Its all explained in the integration guide.

@jimpower You need alsol to connect A of the breakout board to a reference potential, like 1.8 V, as shown in the initial drawing. You must not leave it open, otherwise there will be not signal current.

@antoniovalente Thank you for the instructions and code. Could you please indicate where in the code the data pin (P11) is specified? Also, can you please provide a wiring diagram of the complete circuit with LoPy and N65HVD1780 driver?